ExcitingAds! Search

Directory A-B C-E F-H I-K L-N O-Q R-T U-W X-Z

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are often used, such as based on similarity of DNA or morphology. Presence of specific locally adapted traits may further subdivide species into subspecies.

The commonly used names for plant and animal taxa sometimes correspond to species: for example, "lion," "walrus," and "Camphor tree" – each refers to a species. In other cases common names do not: for example, "deer" refers to a family of 34 species, including Eld's Deer, Red Deer and Elk (Wapiti). The last two species were once considered a single species, illustrating how species boundaries may change with increased scientific knowledge.

Each species is placed within a single genus. This is a hypothesis that the species is more closely related to other species within its genus than to species of other genera. All species are given a binomial name consisting of the generic name and specific name (or specific epithet). For example, Pinus palustris (commonly known as the Longleaf Pine). The taxonomic ranks are life, domain, kingdom, phylum, class, order, family, genus, and species.

A usable definition of the word "species" and reliable methods of identifying particular species are essential for stating and testing biological theories and for measuring biodiversity. Traditionally, multiple examples of a proposed species must be studied for unifying characters before it can be regarded as a species. Extinct species known only from fossils are generally difficult to give precise taxonomic rankings to.

Because of the difficulties with both defining and tallying the total numbers of different species in the world, it is estimated that there are anywhere between 2 and 100 million different species.^[1]

[edit] Binomial convention for naming species

Main article: Binomial nomenclature

In scientific classification, a species is assigned a two-part name, treated as Latin, although roots from any language can be used as well as names of locales or individuals. The genus is listed first (with its leading letter capitalized), followed by a second term: for example, gray wolves belong to the species Canis lupus, coyotes to Canis latrans, golden jackals to Canis aureus, etc., and all of those belong to the genus Canis (which also contains many other species). The name of the species is the whole binomial, not just the second term (which may be called specific name for animals).

Biological classification or scientific classification in biology, is a method by which biologists group and categorize species of organisms. Biological classification is a form of scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis. Modern biological classification has its root in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings since have been revised to improve consistency with the Darwinian principle of common descent. Molecular systematics, which uses DNA sequences as data, has driven many recent revisions and is likely to continue to do so. Biological classification belongs to the science of biological systematics.

[edit] Early systems

[edit] Ancient through medieval times

Current systems of classifying forms of life descend from the thought presented by the Greek philosopher Aristotle, who published in his metaphysical and logical works the first known classification of everything whatsoever, or "being". This is the scheme that gave moderns such words as substance, species and genus and was retained in modified and less general form by Linnaeus.

Aristotle also studied animals and classified them according to method of reproduction, as did Linnaeus later with plants. Aristotle's animal classification was soon made obsolete by additional knowledge and was forgotten.

The philosophical classification is in brief as follows.^[1] Primary substance is the individual being; for example, Peter, Paul, etc. Secondary substance is a predicate that can properly or characteristically be said of a class of primary substances; for example, man of Peter, Paul, etc. The characteristic must not be merely in the individual; for example, being skilled in grammar. Grammatical skill leaves most of Peter out and therefore is not characteristic of him. Similarly man (all of mankind) is not in Peter; rather, he is in man.

Species is the secondary substance that is most proper to its individuals. The most characteristic thing that can be said of Peter is that Peter is a man. An identity is being postulated: "man" is equal to all its individuals and only those individuals. Members of a species differ only in number but are totally the same type.

A biologist is a scientist devoted to and producing results in biology through the study of organisms. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work. Biologists involved in applied research attempt to develop or improve medical, industrial or agricultural processes.

[edit] Training

There are many types of biologists. Some deal with the macroscopic world, and others with the microscopic. There is much overlap between different fields, and it is often hard to classify a biologist as only one of them. Many jobs in biology as a field require an academic degree. A Ph.D. (or equivalent) is generally required to direct independent research, and involves a specialization in a specific area of biology (U.S. Department of Labor). Many biological scientists work in research and development. Some conduct basic research to advance our knowledge of living organisms, including bacteria and other infectious agents. Basic biological research enhances our understanding so that we can develop solutions to human health problems and improve the natural environment. These biological scientists mostly work in government, university, or private industry laboratories, often exploring new areas of research. Many expand on specialized research they started in graduate school.

[edit] Funding

Many research scientists must submit grant proposals to obtain funding for their projects. Colleges and universities, private industry, and Federal Government agencies such as the National Institutes of Health and the National Science Foundation contribute to the support of scientists whose research proposals are determined to be financially feasible and to have the potential to advance new ideas or processes.

[edit] Research

Biological scientists who work in applied research or product development use knowledge gained by basic research to develop new drugs, treatments, and medical diagnostic tests; increase crop yields; and develop new biofuels. They usually have less freedom than basic researchers do to choose the emphasis of their research, and they spend more time working on marketable treatments to meet the business goals of their employers. Biological scientists doing applied research and product development in private industry may be required to describe their research plans or results to nonscientists who are in a position to veto or approve their ideas.